1. Field of the Invention
The present invention relates to an LED illuminating device employing an LED element comprising at least one diode as its light source to produce a wide area of emitted light. The present invention further relates to lighting apparatus employing the LED illuminating device as a light source.
2. Description of the Related Art
To date, numerous light sources using electric power to emit light have been developed with practical applications. In general though, light from these sources has a small area of illumination. In order to achieve effective illumination within a desired area, therefore, these light sources must employ a means for reflecting or diffusing light, such as a reflecting plate, or be used together with a condenser lens or diffusion lens.
By their nature, LEDs (light-emitting diodes) emit light through a light-emission surface without diffusion. In other words, they can emit what are known as parallel light beams. Conventionally, LEDs have primarily been used for indicators or pilot lamps, wherein the light of the LED itself conveys a meaning.
As described in Japanese unexamined patent application publication No. H9-163080, LEDs can also notably be incorporated in light sources for reading facsimile originals or for erasing latent images from photoconductor drums in plain-paper copiers. These light-source devices, well known in the art, are configured of a cylindrical transparent member. The transparent member is provided on one end with a light reader for reading light from an LED and on the other end with a reflecting surface. Lenses are formed in the transparent member by cutting isosceles-triangle shapes in the member with a knurling tool.
However, the light-source devices described in the above publication produce a line-shaped light that is wide along a prescribed direction and narrow in the direction orthogonal to the first direction. Accordingly, these devices are restricted to special uses, such as scanning facsimile originals, and are not appropriate for application in ordinary lamps that must illuminate large areas.
Several methods have been proposed to improve LEDs as a light source for illumination. For example, the published Japanese translation of PCT international publication for patent application No. WO98/13709 describes an illuminating device provided with a flat transparent plate having a plurality of protrusions on its surface and a plurality of point-light sources opposing the opposite surface of the plate. Light irradiated from the point-light sources passes through the transparent plate and is diffracted by the protruding portions as the light is irradiated externally.
However, because the light in devices described in this publication is diffracted and diffused when passing through the transparent member, the amount of light from an already weak LED light source is further reduced, making it difficult to sufficiently illuminate the target.
According to the present invention, there is provided an LED illuminating device which includes a rod-shaped light-guiding member consisting of a translucent material; and an LED element having at least one light emitting diode and disposed at an end of said light-guiding member for emitting lights into said light-guiding member in the longitudinal direction; characterized in that said light-guiding member has a plurality of grooves formed therein arranged along the axial direction of said light-guiding member with a desired distance therebetween for reflecting the lights from said LED element to outside of said light-guiding member.
Preferably, the grooves are disposed only in a desired area adjacent to the end at which the LED element is disposed. Alternately, the grooves are disposed in a desired appropriate interval between adjacent ones, and extending in a direction intersecting an optical axis of the light formed in the light-guiding member at a desired angle.
The grooves may comprise a first group extending along a direction intersecting the optical axis at a first angle, and a second group extending along a direction intersecting the optical axis at a second angle. The distance between adjacent grooves disposed at the end of the light-guiding member at which the LED element is disposed may be larger than that between the adjacent grooves disposed away from the groove pair.
In a preferable aspect of the present invention, the light-guiding member has a configuration of a cylindrical column, part of which is cut-out along a plane intersecting the light axis to form a flat surface and a curved surface opposing the flat surface of the light reflecting section, and wherein the grooves are formed in the planer surface with an appropriate intervals along the longitudinal direction of the light-guiding member and have a reflecting surface for directing the light from the LED element toward the curved surface of the light-guiding member.
The configuration of the cross-section of the light-guiding member may preferably be a combination of part of a circle and a linear line connecting both ends of the circle. Each of the grooves can have a reflecting surface at the bottom thereof for reflecting the light from the LED element to the round surface of the light-guiding member.
The present invention also provides an LED illuminating appliance in the form of a streetlight comprising an illuminating unit including the LED illuminating device to function as a streetlight, which comprises a support post, an illuminating unit supported by the support post, wherein the illuminating unit comprises a housing accommodating a plurality of the LED illuminating devices in parallel with each other, a translucent covering forming a floodlight portion at the front side of the housing, an electric-power source enclosed in the housing for driving the LED illuminating devices.
One of preferable electric power supplying devices is a storage battery and a solar battery panel attached to the pole for supplying electric power to the storage battery, thereby to supply electric power from the storage battery to the LED illuminating devices. Alternatively, the electric power-supplying device comprises a wind power generator attached to the pole and a storage battery for storing electric power from the wind power generator, thereby to supply electric power from the storage battery to the LED illuminating devices.
In another aspect of the present invention, there is provided an LED illuminating appliance in the form of a streetlight comprising an illuminating unit including the LED illuminating device, which comprises an illuminating unit formed as a signboard and a pole for supporting the illuminating unit, wherein the illuminating unit comprises a housing for accommodating a plurality of the LED illuminating devices arranged in parallel with each other, a translucent covering disposed in the front portion of the housing through which light from the LED illuminating devices is directed outside, a storage battery, and a solar cell panel for supplying electric power to the storage battery.
In a further aspect of the present invention, there is provided an LED illuminating appliance in the form of a streetlight comprising an illuminating unit including said LED illuminating device, which comprises an illuminating unit formed as a porch light, wherein said illuminating unit comprises a housing for accommodating a plurality of said LED illuminating devices arranged in parallel with each other, a translucent covering disposed in the front portion of said housing through which the lights from said LED illuminating devices are directed outside and a switch means that is turned on by a signal from a light-receiving element so as to supply electric power to LED illuminating devices when the ambient luminous intensity becomes lower than a predetermined value.
Another LED illuminating appliance according to the present invention can be in the form of a streetlight comprising an illuminating unit including the LED illuminating device, which comprises an illuminating unit comprising a parallel piped casing for accommodating a plurality of the LED illuminating devices arranged in parallel with each other, a translucent covering disposed in the front portion of the housing through which the lights from the LED illuminating devices are directed outside, and a solar cell panel disposed on the upper surface of the housing; and which further comprises a storage battery and a solar cell panel for supplying electric power to the storage battery housed in the housing.
According to the present invention, there also is provided an LED illuminating appliance in the form of a streetlight comprising an illuminating unit including the LED illuminating device, which comprises a cylindrical translucent covering, a cylindrical reflector having a diameter smaller than that of the covering and enclosed therein in a coaxially manner, a plurality of the LED illuminating devices disposed between the covering and the reflector in such manner that the axes of the LED illuminating devices are arranged in a cylindrical plane having a common axis with the reflector and in parallel with each other.
The features and advantages of the present invention will be understood from the following detailed description with reference to the accompanying drawings.